In recent years, as a method of measuring an abdominal fat such as a visceral fat and a subcutaneous fat, a method of using bioelectrical impedance information and physical information of a user is examined. With this method, the bioelectrical impedance is measured with using electrodes in contact with a trunk or the like of the user, and a circumferential length, vertical width, horizontal width, and the like of the trunk are measured as the physical information.
For example, patent document 1 proposes a visceral fat measuring device in which a plurality of electrodes for measuring the bioelectrical impedance is arranged, an electrode support portion capable of being deflected along a shape of the trunk and pressed onto a front surface of an abdominal part of the trunk so as to closely attach the electrodes onto a surface of the trunk, and a pair of arm portions to be brought into contact with both sides of the abdominal part so as to measure the horizontal width of the trunk are provided, and indicators relating to a body fat are calculated from the bioelectrical impedance and the horizontal width of the trunk. Patent document 2 proposes a trunk impedance type body composition monitor for estimating the indicators relating to the body fat from the bioelectrical impedance of the trunk detected by nipping the trunk from the front and back sides by a support portion including a support surface in which a plurality of electrodes is arranged and a pressed portion including a pressed surface facing the support surface, and the vertical width of the trunk measured based on a stop position of the pressed surface.
However, with these technologies, since the pressed portion for closely attaching the electrodes also serves as a measuring unit of the physical information, and the information measured as the physical information of the user is only the horizontal width or the vertical width of the trunk, there is a problem that reliability is insufficient for precision of the information. That is, the trunk of a human being is a part where a shape is easily changed by a breathing action. A section of the abdominal part is changed so that at the time of inhalation, the vertical width is extended and the horizontal width is contracted, and at the time of exhalation, the vertical width is contracted and the horizontal width is extended. Therefore, measurement values are differentiated between a case where the horizontal width or the vertical width of the trunk is measured upon the inhalation and a case where the horizontal width or the vertical width is measured upon the exhalation, so that calculation of the indicators relating to the body fat is varied.
Therefore, in a case where size of the trunk is used as the physical information, it can be said that a breathing state is desirably reflected to size information of the trunk, that is, the breathing state is desirably reflected so as to acquire the size information of the trunk.